A light-sensitive material having a photoconductive layer which is used for making a printing plate by an electrophotographic method is known. For example, a light-sensitive material used for a printing plate comprising a support having provided thereon a metal layer, a photoresist layer and a photoconductive layer as an uppermost layer has been proposed.
Complicated steps which comprise uniformly charging a photoconductive layer, imagewise exposing it to a light to which a photoresist layer is insensitive to prepare an electrostatic latent image on the photoconductive layer, developing the latent image with a toner, fixing or non-fixing a toner image, exposing the photoresist layer under a different condition from that as mentioned above to harden the exposed portion of the photoresist layer, removing the toner image and the photoconductive layer, removing the unhardened portion of the photoresist layer with a solvent, etching a metal layer and removing the photoresist layer remaining on a metal layer are required to prepare a printing plate using the above mentioned light-sensitive material. A high degree of skill is required to prepare a good printing plate. However, the resolving power of the plate is not satisfactory since the developing method of an electrostatic latent image formed on the photoconductive layer is formed by a dry method. Furthermore, clearness of a printing image thus-obtained is not satisfactory because of the removal of a photoresist layer and an etching operation of a metal layer.
To eliminate the above defects, European Patent Application, Published No. 0053362 discloses a method for preparing a lithographic printing plate using the light-sensitive material comprising a conductive support having a hydrophilic surface having provided thereon a positive working light-sensitive layer and a photoconductive insulating layer. The method comprises (1) a step of forming a latent image electrophotographically on the photoconductive layer of the light-sensitive material, (2) a step of developing the latent image with a liquid developer containing developer particles which are opaque to the light to which the positive working light-sensitive layer is light-sensitive, (3) a step of exposing the positive working light-sensitive layer through the developed image thus-obtained in step (2), and (4) a step of selectively removing the areas of the positive working light-sensitive layer which do not have the developed image.
The above method offers improvement on the conventional method with respect to simplification of the steps and resolving power. However, a printing stain is caused when printing is carried out using the printing plate obtained by the above method.